Fix missing pictures in build-a-regression-model-using-scikit-learn-regression-four-ways

[stanciuadrian]

The "Looking for Correlation" section from
https://microsoft.github.io/ML-For-Beginners/#/2-Regression/3-Linear/README?id=build-a-regression-model-using-scikit-learn-regression-four-ways
references 4 images:

• "Average price by month"
• "Scatter plot of Price vs. Day of Year"
• "Bar graph of price vs variety"
• "Scatter plot of Price vs. Day of Year"

The images are not rendered on github.io: